Process for the production of diolefins



; fixed diluent gases is avoided,

- dehydrogenation Patented Sept. 25, 1945 PROCESS FOR THE PRODUCTION OFDIOLEFINS kland, CaliL, assignor to Shell Development Company, SanFrancisco, Calih, a corporation of Delaware :4

Kenneth A. Wright, a

No Drawing. Application January 14, 1944, Serial No. 518,257

14 Claims. (Cl. 260-680) This invention relates to an improved processfor the production of diolefins by catalytic dehydrogenationcharacterized by the use of special catalysts and special hightemperature conditions affording exceptionally high conversion andproduction capacity with excellent yield.

Primary objects of the invention are to provide an improved process forthe production of diolefins, and particularly butadiene, by'catalyticdehydrogenation wherein (1) exceptionally high conversions per passmaybe realized, (2) substantially improved yield of butadiene may beobtained", (3) the production capacity of a given catalytic reactor isexceptionally high, (4) the dehydrogenation is carried out in thepresence of a large excess of steam and the use of vacuum or and (5) thedehydrogenation may be carried out with inexpensive catalysts whichretain their activity over longer periods of time before requiringreplacement.

The importance of diolefins, particularly but-adiene, and thedesirability of having improved methods for their production are wellrecognized. Considerable attention has been given in the past to theproduction of these valuable materials by catalytic dehydrogenationprocesses. Catalytic to produce diolefins differs from most otherdehydrogenation processes in requiring a low partial pressure ofreactantsin the reaction zone. Thus, it is necessary either to carry outthe dehydrogenation under a. substantial vacthe use of very largeamounts uum or to employ large quantities of a diluent.

Operation under a vacuum is very costly. The use of inert diluents todecrease the partial pressure of the reactants usually makes theefficient separation and recovery of the diolefln from the product verydifficult and is a serious disadvantage. Steam is an ideal diluent but,unfortunately, many of the most active dehydrogenation catalysts arepoisoned by water vapors and steam cannotbe employed as a diluent withthem. Also, most of the catalysts are not sufllciently selective intheir action and if steam is used as a diluent they catalyze theoxidation of the reactant by the steam, thus giving low yields. Also,the known catalysts lose their effectiveness in a relatively shortperiod, particularly when steam is employed, and must be frequentlyreplaced.

In order to produce dioleiins by catalytic dehydrogenation using steamas a diluent it is necessary that temperatures above about 580 C. beused and that the catalyst be properly promoted with an alkali metal orits equivalent. Thus, as shown-in appending application Serial No.520,534, filed January 31, 1944, dioleflns may be produced by catalyticdehydrogenation at temperatures catalysts of this type, when usedunrlthjes'e vancement in theart.

above about 580 C. in the presencaof anexcessof steam with an alkalized'iron oxidecatalyst. I preferred alkali is an alkaline compound of potas'sium. In catalysts for dehydrogenationat.high, temperatures in the metalpromoter or its equivalent is e'ssenti'aI sincejifj in its absence thecatalyst loses itsinit'ial ,act vit I, in a few minutes of use. 1.,

It has now been found that the prornqtinge fects of the various alkalimetaliproiiioters" in conditions, are by no means equival nt, 'thatunexpected, different and greatly impfmve rr ui are obtained if thecatalyst is promoted, .Wit

rubidium. Thus, by the simple substitution, rubidium for potassium theconversion per passj s approximately doubled; contrary to expectation,the selectivity is increased and the active life'orj the catalyst isincreased. Thus, the production}; of a given diolefin in a givenreactor, in a givenj time is greatly increased, the produc' iop jper j;pound of reactant is increased, and theproduc}; tion per pound ofcatalyst is increased. In View of the importance of the problem and themag-f nitude of the improvement realized, the present]; invention isconsidered to be an important ad- The process of the invention, since itrequires of steamand-temperatures in the order of 600 C. or above,i sapj plicable in such cases where these'drasticccndi tions are required.Thus, the prqcesscan be ad; vantageously applied for the productionofstyreneff from ethyl benzene and for theiproductio f cyclopentadienefrom cyclopentanei" The pros s is, however, particularlyadvantageousl'fogth "j production of dioleflns, andespeciallyconjug'ated if. dioleflns, from such mono-olefinsas"ar'ecaablef", of being vaporized and heated with stearri' ,to' temperatures ofat least 600 C. witho tial decomposition and contain atileast quaternarycarbon atoms in a straight Thus, the process is particularly; advantagfor the production of such diolefiris as butadi piperylene, isoprene,and the hxadienes. olefin to be dehydrogenated maybe] a, single 'hyidrocarbon or, if desired, a mixtur'eiof bl fins may j be dehydrogenatedto produce a mixture 'jof ,diole'f fins. Also, in some cases a single,diolefln'mayjbc. produced from a mixture of isomeric olefins. For

example, butadiene may be produced froni' either H butene-l or butene-2or a mixture ofjthe "twofi; and isoprene may be produced from:methylfethyl if ethylene, trimethyl ethylene, or isopropyl'ethyl ene ora mixture of these olefins.

presence of steamanau aa der the. preferred conditions of operation theparaflin hydrocarbons are substantially unaffected and. therefore act asinertv diluents;

The catalysts which are applicable at high temperatures in the presenceof large amounts of steam and which are employed in .the process oftheinvention comprise as the primary active component a d'ehydrogenatingoxide of a transition metal of the first transition series 01 theelements (1.. e. V, Cr, Mn, Fe, Co. and Ni), Of these, iron oxide isparticularly effective and suitable, and nickel oxide is the leasteffective. These active dehydrogenating. metal oxides may be presentsingly,.in combination, or in combination with minor amounts of knownstabilizing and/or promoting substances such as oxides of copper, zincand silver, These metal oxides as well as their combinations arereferred to. hereinafter as the dehydrogenating metal oxide component ofrel-- atively highactivity. The catalyst may consist of thedehydrogenating metal oxide of relatively high activity and the rubidiumpromoter, or it may contain minor or major amounts of acarrier,,support, diluent or extender of relatively low catalyticactivity. Thus, the dehydrogenating metal oxide of relatively highactivity may be. employed in combination with a dimcultly reducibleoxide of relatively low catalytic activity such, for instance, as anoxide of aluminum, silicon, zirconium or the like- These components maybe in the form of intimate mixtures, for instance, mixed gels. In othercases the dehydrogenating metal oxide of relatively high catalyticactivity may beincorporated in. relatively minor amounts in the surfaceof a major amount of a relatively inactive support or carrier such asgelsror mixtures of gels o1 silica, alumina, chromi'a, zirconia, etc.,,activated carbon, magnesia, diatomaceous earth, kieselguhr, bauxite, andthe like. Also,

. these various materials of relatively low activity may be combined inmass with the relatively more active dehydrogenating metal oxide toserve as diluents or extenders. Preferred catalysts, however, consistlargely of the dehydrogenating metal oxide of relatively high activity.Thus, a preferred group of catalysts contain at least 50% by weightandpreferably about 70% to 95% of. iron oxide.

The preparationof the catalysts with respect to the preparation of thed'ehydrogenating metal oxides and/or the combining oIv the.dehydrogenating metal oxides with such diluent, extender, supporting orstabilizing materials may be eifected in. any of the conventionalmanners. Thus, the catalysts may be prepared in the wet way byprecipitation methods or by slurry methods, or they may be prepared bythermal decomposition of suitable salts, or they may be prepared by theconventional impregnation methods.

The active dehydrogenating metal oxide or mixture of oxides, or mixturecomprising one or more diluent or carrier materials, is promoted withthe incorporation of a relatively small amount 01' a compound ofrubidium. The rubidium may be incorporated into the catalyst during thepreparation in the'iorm of various rubidium. compounds such. forinstance, as the nitrate, sulfate, carbonate, hydroxide, oxide and thelike. Very suitable and inexpensive rubidium salts are the rubidiumalums. These various compounds; are preferably converted at least inpart to rubidium oxide during the preparation and/or use of. thecatalyst. Halides, when present in the catalyst, appear to exert adetrimental' effect. Since traces oi residual halide anions aredifllcult to remove from the catalyst, halide saltsare. not recommendedin the catalyst preparation. The rubidium may be used alone as thepromoter or it may be used in conjunction with one or more other alkalimetal promoters such, in particular, as potassium and/or caesium. Thus,the rubidium promoter may be advantageously substituted in part "by apotassium promoter. Very suitable mixtures of salts containing potassiumand caesium as well as rubidium may be obtained from the working up ofcertain minerals such as certain lepidolites, certain carnallites, and.certain porphyries containing rubidium. A very suitable material may beprepared, for example, from, the crude mixture of salts of rubidium,caesiu'mand potassium obtained from the mother liquors in the productionof potassium salts. I

The amount of rubidium. required to produce the desired promoting clientis between about 0.8% and 5% by weight of; the relatively activedehydrogenating metal oxide or mixture of metal oxides in the catalyst.This corresponds to between about 0.9% and 5.5% by weight of rubidiumoxide. by weight 0! a relatively inert. diluent such as alumina,magnesia. or the like, the concentration of rubidium in the totalcatalyst is between about 0.4% and 2.5%. If'the rubidium is used inconjunction with potassium, the concentration may be decreased to aboutone-half these amounts. The rubidium promoter may be incorporated intothe catalyst at any suitable stage in the catalyst preparation. Incatalysts which are pelleted or formed into pieces by extrudation orother means, the rubidium is preferably incorporated prior to suchforming operation since catalysts of somewhat higher activity and longerlife are thus obtained. a

In order to maintain the proper state of oxidation ofthedehydrogenatliig metal oxide and to maintain the,catalytic activity,the process of the invention. is can'ied outin the presence of a large.excess of steam. Thus, the mo] ratio 01' steamv to hydrocarbon fed 'tothe reaction zone is at least 2:1 and generally between about 7:1 and3011.

In order to obtain the desired results in the presence, or a largeexcess of steam, the dehydrogenation is carried out at relatively hightemperatures. Thus, the dehydrogenation is carried out at a temperatureat. least as high as 580 C. and generally between about 600C. and 700 C,Somewhat higher temperatures may be employed but are usuallyunnecessary. A preferred method of operation affording high conversionefficiencies consists of adjusting the temperature initially to limitthe conversion. to, say, 35% or 40% and then increasing the temperatureas the process continues to maintain this conversion. Thus, the processmay be initiated with a fresh catalyst at a temperature oi, say, 590 C.and the temperature gradually increase; to, say, 670 C. during the life01' the catalyst. By this method Thus, if the catalyst contains 50%2,885,!- conversion ei'flciencies in,the order of 70% to- An importantadvantage of the process, however, I

is that excellent results may be obtained at atmosplieric pressure; Inview o'tthe"exceptional activity of the described rubidium promotedcatalysts when used under the' described conditions, the process of theinvention; allows excellent con ersion to be obtained quite selectivelyover a considerable range of space'velo'cities. Suitable spacevelocities are; for example, between about 300 and 3000 volumesof'gaseous reactant (N. T. P.) per volumeof catalyst per hour. Aicontacttime affording the optimum results depends upon the particular materialbeing dehydrogenated and the particular conditions chosen within theabove given ranges and may best be determined for any given case bytrial starting with a very-short contact time .andigraduall iincreasingthe contact time untilthe desireddegree of conversion is obtained.

The- .contact time "in. the dehydrogenation of butylenesf'and butadienesby way of example is preferably in the order of, 0.02 to 0.5 second.

The catalystjmayxbe used in any of the conven'tional forms such. aspills, spheres, saddles, extrud-atcs' orirregular fragments of a shapeand size adapted-tor the reaction system to be used. If desired,thelp'rocess may be carried outin a so-called dust catalyst, fluidizedcatalyst or moving bed system.) Excellent results may, however, beobtained. bysimply passing the preheated reactant vapors and-preheatedsteam through agreaction chamber-filled with the catalyst and maintainedati1the. desired temperature and pressure. The steam in the product maybeoeondensed and separated from the converted and unconverted material.The unconverted material may be separated from the product inconventional manners. and recycled.v T

In ma'ny cases it is most advantageous to carry out the; dehydrogenationin'an intermittent manner, that; is, a to: carry out the dehydrogenationin relatively short periods of, for'instance, 1 to 8 hours withintermittent regeneration in the known manner. In such cases theregeneration may be eflectedby simply treating the catalyst The steamand hydrocarbon were passed through the bed 0! catalyst for periods of90 to 105 minutes and thecatalvst was steamed tor about 15 minutes underthe same conditions between each process period. The following resultswere obtainedi' i Butylene Butylene Conversion Cycle reacted gfiagsggeiliclency Percent Percent Percent 1 72 43.4 60.5

74 i 40.9 vs soc t4 A catalyst prepared in the. same manner using thesame materials except that 4.4% or potassium nitrate wasused instead of5.8% of. rubidi'um carbonate, when used at a space velocity of only 1000(other conditions the same), gave the following results:

Butylene Butylene Conversion Cycle reacted aggie efliciency Percent'Pcrcen't Patent 2 73.5 34.3 46.5 4 35.1 52

It will beobserved that by operating according to, the process of theinvention approximately 6% greater conversion to butadiene was obtainedat twice the space velocity. This corresponds-to: increasing theproduction capacity of the reactor. 7

to about 230 of the normal. Y

Aside from the unexpectedlylarge increase in conversion and productioncapacity afforded, the l present process has other important advantages.

. The prior-known catalysts containing potassium become deactivatedduring use at a relatively fast with steam in the absence of thereactantforpa shortperiod at the reaction temperature. Certain of thecatalysts, when employed under the described conditions, do not requiresuch periodic regeneration and when these catalysts are employed thedehydrogenation mayxbe advantaout in a substantially continuous geouslycarried mannerr."

Example A catalyst was prepared asnfollowsrBakers c- P. ie'rric oxidewas slurried ,with 5.8% by weight of rubidium carbonate in aqueous solu-7 tion. The, slurry was evaporated to dryness while i stirring. Thefmasswas heated at 700 C. for 1 hour andithen broken up into 8-20 meshparticles.

This catalyst wasused for the dehydrogenation of a butylene fractionconsisting of butene-l and Mol ratio, steam to butylene 14:1

- lyst is therefore substantiallyeliminated. Any;

rate. Thus, prior-known catalysts are=presently considered to be good ifthey sustain a 20% con version to butadiene under theabove, conditions 3except at a gaseous hourly space..-velocity of 500 It has beendetermined a that one of the causes of this deactivation is due for 300process hours.

to loss of potassium from the catalyst-byvolatilization. The rubidium inthe catalysts used in the process of the present invention is relativelynonvolatile as compared to potassium and is volatilized from'thecatalystat a much slower rate. This cause of decline in the activity of thecatasmall amount of rubidium volatilized in the proc ess of theinvention may be recovered and re-, used. Also, rubidium may berecovered from the 1 spent catalyst bysimple leaching treatment andreused in preparing fresh catalyst. Thus, al-

though rubidium saltsare relatively costly, the

catalyst costs in the operation of the process of the invention are notexpected to be increased appreciably and may, in fact, be lower..

I claim as my invention: y

l. The process forthe productlonof butadiene which comprises contactinga normal butylene in thepresence of at least 2 mols of steam per mol ofmono-olefin at a temperature above '580". C.- at a gaseous hourly spacevelocity between about 300 and 3000 with a catalyst comprising adehydrogenating oxide of iron promoted with rubidium in an amountequivalent to 0.9% and 5.5% by weight calculated as the oxidebased onthe dehydrogenating metal oxide of the catalyst.

2. The process for the production of .butadiene which comprisescontacting a normal butylene in the presence of at least 2 mols oi steamper mol of mono-olefin at a temperature above 580 C. at a gaseous hourlyspace velocity between about 300 and 3000 with a catalyst comprisingiron oxide and magnesia promoted with rubidium in an amount equivalentto 0.9% and 5.5% by weight calculated as the oxide based on thedehydrogenating metal oxide of the catalyst.

3. The process for the production of butadiene which comprisescontacting a normal butylene in the presence of at least 2 mols of steamper mol of mono-olefin at a temperature above 580 C. adjusted to give aconversion to diolefin between 35% and 40% at a gaseous hourly spacevelocity between about 300 and 3000 with a catalyst comprising adehydrogenating oxide of a metal of the first transition series promotedwith rubidium in an amount equivalent to 0.9% and 5.5% by weightcalculated as the oxide based on the dehydrogenating metal oxide of thecatalyst.

4. The process for the production of butadiene which comprisescontacting a normal butylene in the presence of at least 2 mols of steamper mol of mono-olefin at a temperature above 580 C. at a gaseous hourlyspace velocity between about 300 and 3000 with a catalyst comprising adehydrogenating oxide of a metal of the first transition series promotedwith a mixture of alkali metal oxides comprising potassium oxide,rubidium oxide and caesium oxide in an amount equivalent to 0.9% and5.5% by weight calculated as the oxide based on the dehydrogenatingmetal oxide of the catalyst.

5. The process for the production of butadiene which comprisescontacting a normal butylene in the presence of at least 2 mols oi!steam per mol of mono-olefin at a temperature above 580 C. at a gaseoushourly space velocity between I about 300 and 3000 with a catalystcomprising a dehydrogenating oxide of a metal of the first transitionseries promoted with rubidium and potassium in an amount equivalent to0.9% and 5.5% by weight calculated as the oxide based on thedehydrogenatin'g metal oxide of the catalyst.

6. The process for the production of butadiene which comprisescontacting a normal butylene. in the presence of between about '1 and 14mols of steam per mol of mono-olefin at a temperature above 580 C. at agaseous hourly space velocity between about 300 and 3000 with a cata.lyst comprising a dehydrogenating oxide of a metal of the firsttransition series promoted with rubidium in an amount equivalent to 0.9%and 5.5% by weight calculated as the oxide based on the dehydrogenatingmetal oxide of the catalyst.

7. The process for the production of butadiene which comprisescontacting a normal butylene in the presence or at least 2 mols of steamper mol of mono-olefin at a temperature above 580 C. at a gaseous hourlyspace velocity between about 300 and 3000 with a catalyst comprising adehydrogenating oxide of a-metal of the first transition series promotedwith rubidium in an amount equivalent to 0.9% and 5.5% by weightcalculated as the oxide based on the dehydrogenating metal oxide of thecatlayst.

8. A process for the production of a diolefin which comprises contactinga mono-olefin having at least 4 and not more than 5 non-quaternarycarbon atoms in a straight chain in the presence of at least 2 mols ofsteam per mol of mono-olefin at a temperature above 580 C. at a gaseoushourly space velocity between about 300 and 3000 with a catalystcomprising a dehydrogenating oxide of a metal of the first transitiona,ses,4e4

series promoted with a mixture or alkali metal oxides comprisingpotassium oxide, rubidium oxide and caesium oxide in an, amountequivalentto 0.9% and 5.5% by weight. calculated as the oxide based onthe dehydrogenating metal oxide 01' the catalyst, and separating thediolefin from the reaction mixture. i p

9. A process for the production of a diolefin which comprises contactinga mono-olefin having at least 4 and not more than 5 non-quaternarycarbon atoms in a straight'chain in the presence of at least 2 mols ofsteam per mol of mono-olefin at a. temperature above 580C. adiusted togive a conversion to diolefin between 35% and 40% at a gaseous hourlyspace velocity between about 300 and 3000 with a catalyst comprising adehydrogenating oxide of a' metal 01 the first transition seriespromoted with rubidium in an amount equivalent to 0.9% and 5.5% byweight calculated as the oxide based on the dehydrogenating metal oxideof the catalyst, and

separating the diolefin from the reaction mixture.

10. A process for the production 0! a diolefin which comprisescontacting a mono-olefin having at least 4 and not more than 5non-quaternary carbon atoms in a straight'chain in the presence 01' atleast 2 mols of steam per mol of mono-olefin at a temperature. above 580C. at a gaseous hourly space velocity between about 300 and 3000 with acatalyst comprising iron oxide and magnesia promoted with rubidium in anamount equivalent to 0.9% and 5.5% by weight calculated as the oxidebased on the dehydrogenating metal oxide of the catalyst, and separatingthe diolefin from the'reaction mixture.

11. A process for the production of a diolefin which comprisescontacting a mono-olefin having at least 4 and not more than 5non-quaternary carbon atoms in a straight chain in the presence of atleast 2 mols of steam per mol oi mono-olefin at a temperature above 580C. at a gaseous hourly space velocity "between about 300 and 3000 with acatalyst comprising an oxide or iron promoted with rubidium in an amountequivalent to 0.9% and 5.5% by weight calculated as the oxide based onthe dehydrogenating metal oxide or the catalyst, and separating thediolefin from the reaction mixture.

12. A process-for the production of a diolefin which comprisescontacting a mono-olefin having at least 4 and not more than 5non-quater-- nary carbon atoms in a straight chain in the presence of atleast 2 mols of steam per mol of mono-olefin at a temperature above 580C, and at a gaseous hourly space velocity between about 300 and 3000with a catalyst comprising a dehydrogenating oxide oi as metal of thefirst transition series promoted with rubidium and potassium in anamount equivalent to 0.9% and 5.5% by weight calculated as the oxidebased on the dehydrogenating metal oxide of the catalyst, and separatingthe diolefin from the reaction mixture.

13. A process for the production of a diolefin which comprisescontacting a mono-olefin having at least 4 and not more than 5non-quaternary carbon atoms in a straight chain in the aaemae spacevelocity between about 300 and 3000 with a catalyst comprising adehydrogenating oxide 01 a metal of the first transition series promotedwith rubidium in an amount equivalent to 0.9% and 5.5 by weightcalculated as the oxide based on the dehydrogenating metal oxide of thecatalyst, and separating the dioleiin from the reaction mixture.

KENNETH A. WRIGHT.

